The plasma processing apparatus of the present invention can be extensively used for the treatment with a plasma, such as producing semiconductors or semiconductor devices and electronic device materials like liquid crystal devices. Here, however, the description deals with the background art for semiconductor devices.
In the step of producing semiconductor devices, in general, a base member (wafer) for a semiconductor device that is to be treated is subjected to various treatments such as oxidizing treatment, CVD (chemical vapor deposition) treatment, etching treatment, sputtering treatment and the like treatments.
So far, a plasma processing apparatus has in many cases been used for executing a variety of treatments. This is because use of the plasma processing apparatus offers an advantage of a treatment at a low temperature.
So far, a plasma processing chamber for plasma-processing the object has been constituted, usually, by using metallic wall. In this case, ions contained in the plasma generated in the plasma processing chamber impinge on the inner, wall of the plasma processing chamber, whereby the metal constituting the inner wall is sputtered and/or etched often causing the object to be contaminated.
To suppress the sputtering and/or etching, it has heretofore been attempted to treat the inner wall of the plasma processing chamber with Alumite (i.e., form an oxide film on the aluminum surfaces) or to form a ceramic coating on the inner wall.
The treatment with Alumite or the ceramic coating is effective in suppressing the sputtering and/or the etching due to the plasma. In the step of treating with Alumite or forming the ceramic coating, however, a considerable impurity tends to contaminated into the film. Once such impurity is contaminated, it becomes very difficult to clean the inner wall to a sufficient degree after coated with the film despite the inner wall of the plasma processing chamber is subjected to cleaning (by using, for example, hydrofluoric acid).
When the object is treated with the plasma in the plasma processing chamber that has not been cleaned to a sufficient degree, the impurity is physically discharged by sputtering from the inner wall of the plasma processing chamber due to the irradiation with irons produced by the plasma, and deposit on the object giving rise to the occurrence of various problems such as the so-called metal contamination.
The metal contamination tends to become more serious particularly in recent years with an increase in the degree of integration of circuits in the semiconductor devices.